Vacuum tube transmitter system



Nov. 7, 1933. A. cRossLEY 1,933,968

VACUUM TUBE TRANSMITTER SYSTEM Filed Aug. 19, 1927 lulu IN VEN TOR.

; 2106K @oss/.0

/ BY y A TORNEY Patented Nov. 7, 1933 PATENT OFFICE VACUUM TUBE TRANSMITTER SYSTEM Alfred Crossley, Washington, D. C., assignor, by mesne assignments, to Wired Radio, Inc., vNew York, N. Y., a corporation of Delaware Application August 19, 1927. Serial No. 214,053

3 Claims.

My invention relates broadly to electron tube transmitter systems and more particularly to an arrangement of stabilizing circuits for electron tube transmission systems.

One of the objects of my invention is to provide a simplified arrangement of electron tube high frequency amplifier system having means for preventing reaction of currents from the amplifier upon the oscillator system.

Another object of my invention is the provision of a crystal controlled electron tube oscillator system and power amplifier circuit where the power amplifier plate circuit has substantially a capacitative reactance for preventing such a feed-back of energy from the power amplifier circuit to the crystal controlled oscillator system that it will cause the amplifier to oscillate.

Other and further objects of my invention reside in the circuit arrangement of electron tube transmitter as described in the specification hereinafter following by reference to the accompanying drawing, in which:

Figure 1 shows an electron tube transmitter system embodying the principles of myinvention; and Fig. 2 shows a modified circuit arrangement for an electron tube transmitter equipped with the stabilizing circuit of my invention.

My invention is directed to a method of amplifying radio frequency currents which eliminates the necessity of balancing or neutralizing the feed-back currents between Vacuum tube circuits such as are met with in the average transmitter. In addition to this feature the method provides for the elimination of the usual plate circuit tuni ing feature which greatly simplifies the manipulation of the transmitter.

Referring to the drawing, Fig. 1 shows a crystal controlled transmitter which employs a crystal controlled master oscillator and two stages of radio frequency amplification With the usual antenne, system. The novel feature of the transmitter is the use of the impedance 14 shown in Fig. l, which is so constructed that it has a large inductance and a small distributed capacity and its natural period is lower in frequency than that of the master oscillator. With these characteristics the plate circuit of the iirst amplifier stage has a capacitative reactance and as such Will not feed-back power to the master oscillator circuit through the grid plate capacity of the first ampliiier tube with such a phase relation to cause selfoscillations. This elimination of oscillation producing feed-back also means the elimination of trouble experienced with self-oscillations in the amplifier system.

This method of amplification can also be ap- 1" plied Vto transmitters which employ the self-oscillating master oscillator power amplifier system. Such a transmitter is shown in Fig. 2. Vv' ith such a transmitter there is a negligible frequency shift produced when the antenna circuit is tuned for maximum output. This condition is due to the absence yof the oscillation producing feed-back to the master oscillator by virtue of the capacitive load condition in the plate circuit of the iirst amplifier. Practice has demonstrated with the usual amplification methods employing neutralization means in the amplifiers that there is a considerable shift in frequency of the master circuit between a condition Where the amplifier is partially neutralized and when it is wholly neutralized. It therefore can be said that my method eliminates trouble experienced in frequency shift and adjustment for proper balancing of the amplifier together with the additional adjustment for tuning the amplifier for maximum output.

Referring to Fig. 1, the master crystal controlled oscillator consists of the piezo electric crystal element 1, choke coil 2, biasing battery 3, vacuum tube 4, filament battery 5, plate tuned circuit 6, by-pass condenser 7 and the plate battery 8. The first amplifier stage is coupled to the oscillator through the variable tap on the inductance coil of circuit 6 and the condenser 9. A choke coil 10, biasing battery 11, vacuum tube 13, batteries 12 and 16, by-pass condenser 15 and the special impedance or coil system 14 complete the first amplifier stage. The second stage derives its excitation Voltage from the coil system 14 through the condenser 17. The choke coil 18 with battery 28, vacuum tube 19, batteries 2U and 23, oy-pass condenser 22, together with antenna coupling transformer 21 represent the remainder of the second amplifier. The antenna 24 and ground system 25 are tuned to resonance for the desired frequency by the tap 27 on the secondary of the coupling transformer 21.

Fig. 2 is similar to Fig. 1 with the exception of the substitution of the self-oscillating master oscillator for the crystal controlled oscillator. This oscillator consists Vof a Variable condenser 30 and inductance 31, grid leak and stopping condenser 33, vacuum tube 4, batteries 5 and 8, radio frequency choke coil 35 and the by-pass condenser 38. The grids of the oscillator 4 and the los lio

first amplifier 13 are tied together through the condenser1 39, thus providing the necessary coupling for excitation yof the amplifier.

A coupling condenser 36 is connected between the plate electrode of the oscillator 4 and one end of the inductance 31 for facilitating the establishment of oscillatory currents in the circuits of oscillator` tube 4.

The circuit arrangementsl for electron tube transmitters described herein have been found to be highly practical in construction and operation. The transmission system of my invention may be employed for the transmission of signaling energy which may be modulated either telegraphically or telephonically and the circuits may be employed either for space radio or Wired radio broadcasting.

Various modifications of the circuit arrangements of my invention Will be obvious to those skilled in the art and While I have selected for illustration certain of the preferred embodiments of my invention, I desire that it be understood that modifications may be made and that no limitations are intended other than are imposed by the scope of the appended claims.

What I claim as neur and desire to secure by Letters Patent of the United States is as follows:

1. A high frequency amplifying system comprising a vacuum tube having a cathode, an anode, and a grid, means for impressing high frequency electric Waves between said cathode and grid, an energy receiving circuit comprising a condenser and an inductance connected in series between said cathode and anode, and a second circuit between said cathode and anode comprising as its essential elements a source of anode potential in series With a radio frequency choke coil having an inductance and a distributed capacity so related to one another as to give it a natural frequency below the frequency of the Waves to be amplified.

2. A vacuum tube amplifier for radio frequency electric Waves comprising a plurality of vacuum tubes connected in cascade, coupling means connected effectively in shunt with the output circuit of one tube and the input circuit of the succeeding tube, said coupling means comprising in effect a high inductance shunted by a distributed capacitance, the respective values of said inductance and of said capacitance being such as to give said coupling means a resonant frequency beloW that of the Waves to be amplified.

3. A vacuum tube amplifying circuit for amplifying waves over a range of high frequencies comprising a first vacuum tube 'having an output circuit comprising a path offering a low resistance to direct current but a highly inductive and llowly capacitive impedance such that said path is nonresonant to Waves of the frequency to be amplied, a second tube having an input circuit, and means for coupling said output and input circuits together.

ALFRED CROSSLEY. 

